CN114244480B - User equipment, base station and method of operating a transport protocol - Google Patents
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- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
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- H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
- H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
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Abstract
The present invention relates to a user equipment, a base station and a method of operating a transmission protocol. A user equipment operating a transmission protocol for uplink data packet transmission in a communication system, comprising: a receiver receiving a fast retransmission indicator, FRI, indicating that the base station requests retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and a transmitter retransmitting the data packet using the same transmission parameters as have been used for the previously transmitted data packet.
Description
The application is that the application date is 2016, 5, 13 and the application number is: 201680085617.5, filed under the name "a user equipment, a base station and a method for uplink data packet transmission".
Technical Field
The present disclosure relates to a method for operating a transmission protocol for uplink data packet transmission in a communication system. The present disclosure also provides a user equipment and a base station for participating in the methods described herein.
Background
Long Term Evolution (LTE)
Third generation mobile systems (3G) based on WCDMA radio access technology are being widely deployed worldwide. The first step in enhancing or evolving such technologies requires the introduction of High Speed Downlink Packet Access (HSDPA) and enhanced uplink (also known as High Speed Uplink Packet Access (HSUPA)) to provide highly competitive radio access technologies.
In order to prepare for further increased user demands and to be competitive with new radio access technologies, 3GPP introduced a new mobile communication system called Long Term Evolution (LTE). LTE is designed to meet the needs of operators for high-speed data and media transport and high-capacity voice support for the next decade. The ability to provide high bit rates is a key measure for LTE.
The Work Item (WI) specification of Long Term Evolution (LTE), known as evolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN), is finalized as release 8 (LTE rel.8). LTE systems represent efficient packet-based radio access and provide a radio access network with completely IP-based functionality with low latency and low cost. In LTE, scalable multiple transmission bandwidths are specified, such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0MHz, in order to achieve flexible system deployment using a given spectrum. In the downlink, orthogonal Frequency Division Multiplexing (OFDM) based radio access is employed because of its inherent immunity to multipath interference (MPI) due to the low symbol rate, the use of Cyclic Prefixes (CPs) and their affinity to different transmission bandwidth arrangements. In the uplink, single carrier frequency division multiple access (SC-FDMA) based radio access is employed because the provision of wide area coverage takes precedence over the increase of peak data rates in view of the limited transmit power of the User Equipment (UE). Many key packet radio access technologies are employed, including Multiple Input Multiple Output (MIMO) channel transmission techniques, and an efficient control signaling structure is implemented in LTE release 8/9.
LTE architecture
The overall LTE architecture is shown in fig. 1. The E-UTRAN consists of eNodeB, providing E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations to a User Equipment (UE). An eNodeB (eNB) host (host) includes a Physical (PHY) layer, a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a Packet Data Control Protocol (PDCP) layer for user plane header compression and ciphering functions. It also provides Radio Resource Control (RRC) functions corresponding to the control plane. It performs many functions including radio resource management, admission control, scheduling, enhancement of negotiated uplink quality of service (QoS), cell information broadcast, encryption/decryption of user and control plane data, and compression/decompression of downlink/uplink user plane packet headers. The enodebs are interconnected to each other by an X2 interface.
The eNodeB is also connected to the EPC (evolved packet core) through an S1 interface, more specifically to the MME (mobility management entity) through an S1-MME and to the Serving Gateway (SGW) through an S1-U. The S1 interface supports a many-to-many relationship between MME/serving gateway and eNodeB. The SGW routes and forwards user data packets while also acting as a mobility anchor for the user plane during inter-eNodeB handover and as an anchor for mobility between LTE and other 3GPP technologies (terminating the S4 interface and relaying traffic between the 2G/3G system and the PDN GW). For idle state user equipment, when downlink data arrives at the user equipment, the SGW terminates the downlink data path and triggers paging. It manages and stores user equipment content such as parameters of IP bearer services or network internal routing information. It also performs duplication of user traffic in the case of lawful interception.
The MME is a key control node for the LTE access network. It is responsible for idle mode user equipment tracking and paging procedures, including retransmissions. It relates to bearer activation/deactivation processing and is also responsible for selecting the SGW of the user equipment at initial attach and at intra-LTE handover involving Core Network (CN) node relocation. It is responsible for authenticating the user (by interacting with the HSS). Non-Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generating and assigning temporary identities to user equipments. It checks the authorization of the user equipment to camp on the Public Land Mobile Network (PLMN) of the service provider and enforces the user equipment roaming restrictions. The MME is the termination point for ciphering/integrity protection for NAS signaling in the network and handles security key management. The MME also supports legal signaling interception. The MME also provides control plane functions for mobility between LTE and 2G/3G access networks, where the S3 interface terminates from the SGSN at the MME. The MME also terminates the S6a interface for the home HSS in order to roam the user equipment.
Component carrier structure in LTE
The downlink component carriers of the 3GPP LTE system are subdivided in the time-frequency domain in so-called subframes. In 3GPP LTE, each subframe is divided into two downlink slots as shown in FIG. 2, where the first downlink slot includes a control channel region (PDCCH region) within the first OFDM symbol. Each subframe consists of a given number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (release 8)), where each OFDM symbol spans the entire bandwidth of a component carrier. Thus, an OFDM symbol is composed of a plurality of modulation symbols transmitted on respective subcarriers. In LTE, the transmission signal in each slot is composed ofSubcarrier sum/>Resource grid of symbols. /(I)Is the number of resource blocks within the bandwidth. The amount/>Depends on the downlink transmission bandwidth configured in the cell and should be satisfiedWherein/>And/>The minimum downlink bandwidth and the maximum downlink bandwidth, respectively, supported by the current version of the specification. /(I)Is the number of subcarriers within one resource block. For normal cyclic prefix subframe structure,/>And/>
Assuming a multicarrier communication system employing OFDM, for example, as used in 3GPP Long Term Evolution (LTE), for example, the smallest unit of resources that can be allocated by the scheduler is one "resource block". A Physical Resource Block (PRB) is defined as consecutive OFDM symbols (e.g., 7 OFDM symbols) in the time domain and consecutive subcarriers (e.g., 12 subcarriers for component carriers) in the frequency domain as illustrated in fig. 2. In 3GPP LTE (release 8), therefore, the physical resource block consists of resource elements corresponding to one slot in the time domain and 180kHz in the frequency domain (see, e.g., section 6.2 of the 3GPP TS 36.211,"Evolved Universal Terrestrial Radio Access(E-UTRA);Physical Channels and Modulation(Release 8)", current version 13.0.0 (NPL 1), available from http:// www.3gpp.org for more details of the downlink resource grid and incorporated herein by reference).
One subframe consists of two slots such that 14 OFDM symbols are present in the subframe when a so-called "normal" CP (cyclic prefix) is used, and 12 OFDM symbols are present in the subframe when a so-called "extended" CP is used. For the sake of terminology, hereinafter, time-frequency resources equivalent to the same consecutive subcarriers across a complete subframe are referred to as "resource block pairs" or equivalent "RB pairs" or "PRB pairs".
The term "component carrier" refers to a combination of several resource blocks in the frequency domain. In future versions of LTE, the term "component carrier" is no longer used; instead, the term is changed to "cell", which refers to a combination of downlink and optionally uplink resources. The link between the carrier frequency of the downlink resource and the carrier frequency of the uplink resource is indicated in the system information transmitted on the downlink resource.
Similar assumptions on the component carrier structure will apply to later versions as well.
Carrier aggregation in LTE-A for supporting wider bandwidths
Worldwide radio conference (World Radio communication Conference, WRC-07) in 2007 determined the spectrum for IMT-Advanced. Although the overall spectrum for IMT-Advanced is decided, the actually available frequency bandwidth varies according to each region or country. But after the available spectrum profile decision, the standardization of the radio interface starts with the third generation partnership project (3 GPP). At the 3GPP TSG RAN#39 conference, a study item description about "Further Advancements for E-UTRA (LTE-Advanced)" was approved. The research project covers technical components to be considered for E-UTRA evolution, for example to meet the requirements for IMT-Advanced.
The bandwidth that the LTE-Advanced system can support is 100MHz, whereas the LTE system can only support 20MHz. Today, the lack of radio spectrum has become a bottleneck for wireless network development and thus it is difficult to find a frequency band that is wide enough for LTE-Advanced systems. Thus, there is an urgent need to find a way to obtain a wider radio frequency spectrum band, where a possible answer is a carrier aggregation function.
In carrier aggregation, two or more component carriers are aggregated in order to support a wider transmission bandwidth up to 100 MHz. Several cells in an LTE system are aggregated into one wider channel in an LTE-Advanced system that is wide enough for 100MHz, even though these cells in LTE may be in different frequency bands.
All component carriers may be configured to be LTE release 8/9 compatible at least when the bandwidth of the component carrier does not exceed the bandwidth supported by the LTE release 8/9 cell. Not all component carriers aggregated by the user equipment must be possible release 8/9 compatible. Existing mechanisms (e.g., restrictions) may be used to avoid camping on component carriers for Rel-8/9 (release 8/9) user equipment.
The user equipment may receive or transmit on one or more component carriers (corresponding to multiple serving cells) at the same time depending on its capabilities. LTE-a release 10 user equipment with reception and/or transmission capabilities for carrier aggregation may receive and/or transmit simultaneously on multiple serving cells, whereas LTE release 8/9 user equipment may only receive and transmit on a single serving cell if the structure of the component carrier complies with the release 8/9 specification.
Carrier aggregation is supported for both continuous and discontinuous component carriers, where each component carrier is limited to a maximum of 110 resource blocks in the frequency domain (using 3GPP LTE (release 8/9) numerology (numerology)).
It is possible to configure 3GPP LTE-a (release 10) compliant user equipment to aggregate different numbers of component carriers originating from the same eNodeB (base station) and possibly different bandwidths in the uplink and downlink. The number of downlink component carriers that can be configured depends on the downlink aggregation capability of the UE. In contrast, the number of uplink component carriers that can be configured depends on the uplink aggregation capability of the UE. Mobile terminals having more uplink component carriers than downlink component carriers may not be currently configured. In a typical TDD deployment, the number of component carriers and the bandwidth of each component carrier in the uplink and downlink are the same. Component carriers originating from the same eNodeB need not provide the same coverage.
The spacing between the center frequencies of the continuously aggregated component carriers should be a multiple of 300 kHz. This is to be compatible with the 100kHz frequency raster of 3GPP LTE (release 8/9) and at the same time maintain orthogonality of the sub-carriers with 15kHz spacing. Depending on the aggregation scenario, an n×300kHz interval may be facilitated by inserting a small number of unused subcarriers between consecutive component carriers.
The nature of multiple carrier aggregation is only exposed to the MAC layer. For both uplink and downlink, one HARQ entity is needed in the MAC for each aggregated component carrier. There is at most one transport block per component carrier (in case SU-MIMO is not present in the uplink). The transport block and its potential HARQ retransmissions need to be mapped on the same component carrier.
When carrier aggregation is configured, the mobile terminal has only one RRC connection with the network. In RRC connection establishment/reestablishment, one cell provides security input (one ECGI, one PCI and one ARFCN) and non-access stratum mobility information (e.g., TAI) similar to that in LTE release 8/9. After RRC connection establishment/re-establishment, the component carrier corresponding to the cell is referred to as a downlink primary cell (PRIMARY CELL, PCELL). In the connected state, each user equipment is always configured with one and only one downlink PCell (DL PCell) and one uplink PCell (UL PCell). Within the configured component carrier set, other cells are referred to as Secondary cells (scells); wherein the carriers of the SCell are downlink secondary component carriers (DL SCCs) and uplink secondary component carriers (UL SCCs). For one UE, at most five serving cells, including PCell, may be configured.
MAC layer/entity, RRC layer, physical layer
The LTE layer 2 user plane/control plane protocol stack includes four sublayers, RRC, PDCP, RLC and MAC. The Medium Access Control (MAC) layer is the lowest sublayer in the layer 2 architecture of the LTE radio protocol stack and is defined by, for example, 3GPP technical standard TS 36.321, current release 13.0.0. The connection with the lower physical layer is through a transport channel and the connection with the upper RLC layer is through a logical channel. Thus, the MAC layer performs multiplexing and demultiplexing between logical channels and transport channels: the MAC layer of the transmitting side constructs a MAC PDU (called a transport block) from the MAC SDU received through the logical channel, and the MAC layer of the receiving side recovers the MAC SDU from the MAC PDU received through the transport channel.
The MAC layer provides data transfer services to the RLC layer through logical channels (see sub-clauses 5.4 and 5.3 of TS 36.321), which are either control logical channels carrying control data (e.g., RRC signaling) or traffic logical channels carrying user plane data. On the other hand, data from the MAC layer is exchanged with the physical layer through a transport channel, which is classified as downlink or uplink. The data is multiplexed into the transport channel depending on the manner in which it is transmitted over the air.
The physical layer is responsible for actually transmitting data and control information via the air interface, i.e. the physical layer carries all information from the MAC transport channel over the air interface on the transmission side. Some important functions performed by the physical layer include coding and modulation, link Adaptation (AMC), power control, cell search (for initial synchronization and handover purposes), and other measurements for the RRC layer (within the LTE system and between systems). The physical layer performs transmission based on transmission parameters such as a modulation scheme, a coding rate (i.e., modulation and coding scheme, MCS), the number of physical resource blocks, and the like. More information about physical layer functionality can be found in current version 13.0.0 of 3GPP technical standard 36.213, which is incorporated herein by reference.
A Radio Resource Control (RRC) layer controls communications between UEs and enbs at a radio interface and mobility of UEs moving across several cells. The RRC protocol also supports the transfer of NAS information. For UEs in rrc_idle, RRC supports notification of incoming calls from the network. The RRC connection control covers all procedures related to establishment, modification and release of RRC connection including paging, measurement configuration and reporting, radio resource configuration, initial security activation, and establishment of Signaling Radio Bearers (SRBs) and radio bearers carrying user data (data radio bearers, DRBs).
The Radio Link Control (RLC) sub-layer mainly includes ARQ functionality and supports data segmentation and concatenation, i.e. the RLC layer performs framing of RLC SDUs to put them in the size indicated by the MAC layer. The latter two minimize protocol overhead independent of data rate. The RLC layer is connected to the MAC layer via a logical channel. Each logical channel carries a different type of traffic. The layer above the RLC layer is typically the PDCP layer, but in some cases it is the RRC layer, i.e. RRC messages sent on the logical channels BCCH (broadcast control channel), PCCH (paging control channel) and CCCH (common control channel) do not require security protection and therefore bypass the PDCP layer directly into the RLC layer. The main services and functions of the RLC sublayer include:
Transmitting an upper layer PDU supporting AM, UM or TM data transmission;
Error correction by ARQ;
Segmentation according to the size of the TB;
Re-segmentation when necessary (e.g. when radio quality (i.e. supported TB size) changes)
The connection for SDUs of the same radio bearer is FFS;
Delivering upper layer PDUs in order;
Duplicate item detection;
Protocol error detection and recovery;
SDU discard;
Reset
The ARQ functionality provided by the RLC layer will be discussed in more detail in later sections.
Uplink access scheme for LTE
For uplink transmissions, power efficient user terminal transmissions are needed to maximize coverage. Single carrier transmission combined with FDMA with dynamic bandwidth allocation has been chosen as the evolved UTRA uplink transmission scheme. The main reason for preference for single carrier transmission compared to multi-carrier signal (OFDMA) is lower peak-to-average power ratio (PAPR), and corresponding improved power amplifier efficiency and improved coverage (higher data rate for a given terminal peak power). During each time interval, the eNodeB assigns the user unique time/frequency resources for transmitting user data, thereby ensuring intra-cell orthogonality. Orthogonal access in the uplink improves spectral efficiency by cancelling intra-cell interference. Processing interference due to multipath propagation at a base station (eNode B) is aided by inserting a cyclic prefix in the transmitted signal.
The basic physical resources for data transmission consist of frequency resources of size bwgrants during one time interval (e.g., subframe) over which coded information bits are mapped. It should be noted that a subframe, also referred to as a Transmission Time Interval (TTI), is the minimum time interval for user data transmission. It is possible to assign the frequency resource bwgrants to users over a longer period of time than one TTI through concatenation of subframes.
Layer 1/layer 2 control signaling
In order to inform scheduled users of their allocation status, transport format and other data related information (e.g. HARQ), L1/L2 control signaling needs to be sent on the downlink together with the data. Control signaling needs to be multiplexed with downlink data in a subframe (assuming that user allocation can change from subframe to subframe). Here, it should be noted that the user allocation may also be performed on a TTI (transmission time interval) basis, where the TTI length is a multiple of the sub-frames. The TTI length may be fixed in the service area for all users, may be different for different users, or may even be dynamic for each user. In general, L1/L2 control signaling need only be sent once per TTI. L1/L2 control signaling is sent on the Physical Downlink Control Channel (PDCCH). It should be noted that for the assignment of uplink data transmission, UL grants are also sent on PDCCH.
Hereinafter, detailed L1/L2 control signaling information signaled for DL allocation and uplink assignment is described below:
Downstream data transmission
Along with the downlink packet data transmission, L1/L2 control signaling is sent on a separate physical channel (PDCCH). Such L1/L2 control signaling typically contains information about:
physical resource(s) on which data is transmitted (e.g., subcarriers or subcarrier blocks in the case of OFDM, codes in the case of CDMA). This information allows the UE (receiver) to identify the resources on which to send the data.
Transport format for transmission. This may be the transport block size (payload size, information bit size), MCS (modulation and coding scheme) level, spectral efficiency, code rate, etc. of the data. This information, typically along with the resource allocation, allows the UE (receiver) to identify the information bit size, modulation scheme and code rate in order to begin demodulation, de-rate matching and decoding processes. In some cases, the modulation scheme may be explicitly signaled.
Hybrid ARQ (HARQ) information:
Number o: hybrid ARQ process allowing a UE to identify data mapped thereon
Omicron sequence number or new data indicator: allowing a UE to identify whether a transmission is a new packet or a retransmission packet
O redundancy and/or constellation version: telling the UE which hybrid ARQ redundancy version to use (required for de-rate matching) and/or which modulation constellation version to use (required for demodulation)
UE identity (UE ID): tells the L1/L2 control signaling which UE to use. In a typical implementation, this information is used to mask the CRC of L1/L2 control signaling in order to prevent other UEs from reading this information.
Uplink data transmission
To enable uplink packet data transmission, L1/L2 control signaling is sent on the downlink (PDCCH) to tell the UE about the transmission details. Such L1/L2 control signaling typically contains information about:
physical resource(s) on which the UE should transmit data (e.g., subcarrier or subcarrier block in case of OFDM, code in case of CDMA).
Transport format, UE shall be used for transmission. This may be the transport block size (payload size, information bit size), MCS (modulation and coding scheme) level, spectral efficiency, code rate, etc. of the data. This information, typically together with the resource allocation, allows the UE (receiver) to identify the information bit size, modulation scheme and code rate in order to start the modulation, rate matching and coding process. In some cases, the modulation scheme may be explicitly signaled.
Hybrid ARQ information:
Number o: telling the UE which hybrid ARQ process it should pick data from
Omicron sequence number or new data indicator: telling the UE to send a new packet or to retransmit a packet
O redundancy and/or constellation version: telling the UE which hybrid ARQ redundancy version to use (required for rate matching) and/or which modulation constellation version to use (required for modulation)
UE identity (UE ID): tells which UE should send the data. In a typical implementation, this information is used to mask the CRC of L1/L2 control signaling in order to prevent other UEs from reading this information.
How to accurately transmit the above-mentioned pieces of information has several different styles. In addition, the L1/L2 control information may also contain additional information or some information may be omitted. For example:
in case of synchronous HARQ protocol, HARQ process numbers may not be required
Redundancy and/or constellation versions may not be needed if additional combining is used (the same redundancy and/or constellation version is used all the time) or if the redundancy and/or constellation version sequences are predefined.
The power control information may additionally be included in the control signaling
MIMO-related control information, such as e.g. precoding, may additionally be included in the control signaling.
In the case of multiple codewords, MIMO transport formats and/or HARQ information for multiple codewords may be included.
For uplink resource assignment (PUSCH) signaled on PDCCH in LTE, the L1/L2 control information does not contain HARQ process number, since the synchronous HARQ protocol is employed for LTE uplink. The HARQ process to be used for uplink transmission is given by timing. Furthermore, it should be noted that Redundancy Version (RV) information is encoded jointly with transport format information, i.e. RV information is embedded in the Transport Format (TF) field. The TF and MCS fields have a size of, for example, 5 bits, which corresponds to 32 entries. 3 TF/MCS table entries are reserved for indicating RV 1, 2 or 3. The remaining MCS table entries are used to signal an MCS level (TBS) that implicitly indicates RV 0. The size of the CRC field of the PDCCH is 16 bits. More detailed information about control information for uplink resource allocation on PUSCH can be found in TS36.212 section 5.3.3 and TS36.213 section 8.6.
For downlink assignments (PDSCH) signaled on PDCCH in LTE, redundancy Versions (RVs) are signaled separately in two-bit fields. Furthermore, the modulation order information is encoded jointly with the transport format information. Similar to the uplink case, a 5-bit MCS field is signaled on the PDCCH. The 3 entries are reserved to signal explicit modulation order without providing transport format (transport block) information. For the remaining 29 entries, modulation order and transport block size information is signaled. More detailed information about control information for uplink resource allocation on PUSCH can be found in section 5.3.3 of TS36.212 and section 7.1.7 of TS36.213, which are incorporated herein by reference.
E-UTRAN measurement-measurement gap
The E-UTRAN may configure the UE to report measurement information, e.g., to support control of UE mobility. The corresponding measurement configuration element may be signaled by a RRCConnectionReconfiguration message. For example, the measurement gap defines a period of time when no uplink or downlink transmission is to be scheduled, so that the UE can perform measurements. Measuring gaps is common to all gap-assisted measurements. Inter-frequency measurements may require configuration of measurement gaps, depending on the capabilities of the UE (e.g., whether it has dual receivers). The UE identifies an E-UTRA cell operating on a carrier frequency different from the serving cell. Inter-frequency measurements, including cell identification, or performed during periodic measurement gaps, unless the UE has more than one receiver. The network may configure two possible gap modes, each gap mode having a length of 6ms: in gap mode #0, the gap occurs every 40ms, while in gap mode #1, the gap occurs every 80 ms.
For example, a Reference Signal Received Power (RSRP) is measured by a UE over a measurement period by measuring cell-specific reference signals within a bandwidth.
ARQ/Hybrid ARQ (HARQ) scheme
In LTE, there are two levels of retransmissions for providing reliability, namely HARQ for the MAC layer and outer ARQ for the RLC layer. The RLC retransmission mechanism is responsible for providing error-free data delivery to higher layers. To achieve this, the (re) transmission protocol operates between RLC entities in the receiver and the sender, e.g. in acknowledged mode. Although the RLC layer will be able to handle transmission errors due to noise, unpredictable channel variations, etc., this is in most cases handled by the HARQ retransmission protocol of the MAC layer. Therefore, it may seem superfluous to use the retransmission mechanism first in the RLC layer. This is not the case and the use of RLC and MAC based retransmission mechanisms is in fact well motivated by the difference in feedback signaling. For example, the RLC-ARQ mechanism is responsible for handling NACK-to-ACK errors that may occur with the MAC HARQ mechanism.
A common technique for error detection and correction in packet transmission systems over unreliable channels is known as hybrid automatic repeat request (HARQ). Hybrid ARQ is a combination of Forward Error Correction (FEC) and ARQ. If the FEC encoded packet is transmitted and the receiver fails to decode the packet correctly (errors are typically checked by CRC, cyclic redundancy check), the receiver requests retransmission of the packet.
RLC retransmission protocol
When the RLC is configured to request retransmission of a missing PDU, it is said to operate in Acknowledged Mode (AM). This is similar to the corresponding mechanism used in WCDMA/HSPA.
In general, RLC has three modes of operation: transparent Mode (TM), unacknowledged Mode (UM), acknowledged Mode (AM). Each RLC entity is configured by the RRC to operate in one of these modes.
In the transparent mode, no protocol overhead is added to RLC SDUs received from higher layers. In special cases, transmissions with limited segmentation/reassembly capabilities may be implemented. Whether segmentation/reassembly is used or not, negotiations must be performed during radio bearer setup. Transparent mode is used for example for very delay sensitive services like speech.
In unacknowledged mode, data delivery cannot be guaranteed since no retransmission protocol is used. The PDU structure includes sequence numbers for integrity observations in higher layers. Based on the RLC sequence numbers, the receiving UM RLC entity may perform reordering of the received RLC PDUs. Segmentation and concatenation are provided by means of header fields added to the data. The RLC entity in unacknowledged mode is unidirectional in that no association is defined between uplink and downlink. If erroneous data is received, the corresponding PDU is discarded or marked depending on the configuration. In the transmitter, RLC SDUs that were not transmitted for a specific time specified by the timer are discarded and removed from the transmission buffer. RLC SDUs received from higher layers are segmented/concatenated into RLC PDUs at the sender side. On the receiver side, reorganization is performed accordingly. Unacknowledged mode is used for services where error free delivery is less important than short delivery times, e.g., for certain RRC signaling procedures, cell broadcast services such as MBMS and voice over IP (VoIP).
In acknowledged mode, the RLC layer supports error correction by means of automatic repeat request (ARQ) protocols and is typically used for IP based services such as file transfer, where error free data delivery is a major concern. RLC retransmissions are for example based on RLC status reports, i.e. ACK/NACK, received from peer RLC receiving entities. The acknowledged mode is designed to reliably transport packet data by retransmission in the presence of high air interface error rates. In case of PDU errors or losses, the sender retransmits upon receiving RLC status reports from the receiver.
ARQ is used as a retransmission scheme for retransmitting erroneous or lost PDUs. For example, the receiving RLC entity may identify the missing PDU by monitoring the incoming sequence number. Then, an RLC status report may be generated at the receiving RLC side and fed back to the transmitting RLC entity, thereby requesting retransmission of the lost or unsuccessfully decoded PDU. The RLC status report may also be polled by the sender, i.e., the polling function is used by the RLC sender to obtain a status report from the RLC receiver in order to inform the RLC sender of the reception buffer status. The status report provides a positive Acknowledgement (ACK) or negative acknowledgement information (NACK) on the RLC data PDUs or a portion thereof until the last RLC data PDU for which HARQ reordering is complete. The RLC receiver triggers a status report if its polling field is set to a PDU of "1" or an RLC data PDU loss is detected. Some triggers that trigger polling of RLC status reports in RLC transmitters are defined in current version 13.0.0 of sub-clause 5.2.3 of TS36.322 incorporated herein by reference. In the transmitter, the transmission of PDUs is only allowed within the transmission window, and the transmission window is updated only by RLC status report. Thus, if RLC status report is delayed, the transmission window cannot advance and the transmission may get stuck.
The receiver transmits an RLC status report to the sender when triggered.
As already mentioned above, in addition to data PDU delivery, control PDUs can also be signaled between peer entities.
MAC HARQ protocol
The MAC layer includes HARQ entities that are responsible for transmitting and receiving HARQ operations. The transmit HARQ operation includes transmission and retransmission of transport blocks, and reception and processing of ACK/NACK signaling. The receive HARQ operation includes reception of transport blocks, combination of received data, and generation of ACK/NACK signaling. To achieve continuous transmission while decoding the previous transport block, up to eight HARQ processes in parallel are used to support multi-process "stop-and-wait" (SAW) HARQ operations. Each HARQ process is responsible for separate SAW operations and manages separate buffers.
The feedback provided by the HARQ protocol is either an Acknowledgement (ACK) or a Negative Acknowledgement (NACK). The ACK and NACK are generated depending on whether the transmission can be received correctly (e.g., whether the decoding was successful). Furthermore, in HARQ operation, the eNB may send different encoded versions from the original transport block in retransmissions so that the UE may employ Incremental Redundancy (IR) combining to obtain additional coding gain via the combining gain.
If the FEC encoded packet is transmitted and the receiver fails to decode the packet correctly (errors are typically checked by CRC, cyclic redundancy check), the receiver requests retransmission of the packet. In general (and throughout this document), the transmission of additional information is referred to as a "(packetized) retransmission", and such retransmission may, but need not, mean the transmission of the same encoded information; it may also mean the transmission of any information (e.g. additional redundancy information) belonging to the packet, e.g. by using different redundancy versions.
In general, HARQ schemes can be classified as synchronous or asynchronous, where the retransmission in each case is adaptive or non-adaptive. Synchronous HARQ means that retransmission of a transport block for each HARQ process occurs at a predefined (periodic) time relative to the initial transmission. Thus, no explicit signaling is required to indicate the retransmission schedule, or e.g. the HARQ process number, to the receiver, as it can be deduced from the transmission timing.
In contrast, asynchronous HARQ allows retransmissions to occur at any time relative to the initial transmission, which provides flexibility in scheduling retransmissions based on air interface conditions. But in this case additional explicit signaling is required to indicate e.g. HARQ processes to the receiver in order to allow correct combining and protocol operation. In the 3GPP LTE system, HARQ operation with eight processes is used.
In LTE, asynchronous adaptive HARQ is used for the downlink and synchronous HARQ is used for the uplink. In the uplink, the retransmission may be either adaptive or non-adaptive, depending on whether new signaling of the transmission properties is provided, e.g. in the uplink grant.
In uplink HARQ protocol operation (i.e. for acknowledging uplink data transmissions), there are two different options as to how to schedule retransmissions. Retransmissions are explicitly scheduled either by NACK "scheduling" (also called synchronous non-adaptive retransmission) or by the network by sending PDCCH (also called synchronous adaptive retransmission).
In case of synchronous non-adaptive retransmissions, the retransmissions will use the same parameters as the previous uplink transmission, i.e. the retransmissions will be signaled on the same physical channel resources, using the same modulation scheme/transport format, respectively. But the redundancy versions will change, i.e. cycle through the predefined redundancy version sequences 0, 2,3, 1.
Since synchronous adaptive retransmissions are explicitly scheduled via the PDCCH, it is possible for the eNodeB to change certain parameters for the retransmissions. Retransmissions may be scheduled, for example, on different frequency resources to avoid fragmentation in the uplink, or the eNodeB may change the modulation scheme, or alternatively indicate to the user equipment what redundancy versions to use for retransmissions. It should be noted that HARQ feedback (ACK/NACK) and PDCCH signaling occur at the same timing for UL HARQ FDD operation. Thus, the user equipment only needs to check if a synchronous non-adaptive retransmission is triggered once (i.e. only NACK is received) or if the eNodeB requests a synchronous adaptive retransmission (i.e. PDCCH is also signaled).
The PHICH carries HARQ feedback that indicates whether the eNodeB has correctly received the transmission on PUSCH. The HARQ indicator is set to 0 for positive Acknowledgements (ACKs) and to 1 for Negative Acknowledgements (NACKs). PHICH carrying ACK/NACK message for uplink data transmission may be transmitted simultaneously with physical downlink control channel PDCCH for the same user terminal. With such simultaneous transmission, the user terminal can determine what the PDCCH indicates to the terminal, i.e., whether to perform a new transmission (a new UL grant with handover NDI) or a retransmission (referred to as an adaptive retransmission) (a new UL grant without handover NDI), regardless of PHICH content. When the PDCCH for the terminal is not detected, PHICH content indicates UL HARQ behavior of the terminal, as summarized below.
NACK: the terminal performs non-adaptive retransmissions, i.e. retransmissions on the same uplink resources as previously used by the same HARQ process
ACK: the terminal does not perform any uplink retransmission and keeps the data in the HARQ buffer for that HARQ process. Further transmissions for that HARQ process need to be explicitly scheduled by a subsequent grant of PDCCH. Until such authorization is received, the terminal is in a "suspended state".
As shown in table 11 below:
The scheduling timing of the uplink HARQ protocol in LTE is exemplarily shown in fig. 3. The eNB sends a first uplink grant 301 to the UE on the PDCCH, in response to which the UE sends first data 302 to the eNB on the PUSCH. The timing between PDCCH uplink grant and PUSCH transmission is currently fixed at 4ms. After receiving the first data transmission 302 from the UE, the eNB sends feedback information (ACK/NACK) and possibly UL grant 303 for the received transmission to the UE (alternatively, when the UL transmission is successful, the eNB may have triggered a new uplink transmission by sending a suitable second uplink grant). The timing between PUSCH transmission and the corresponding PHICH carrying feedback information is also currently fixed to 4ms. Thus, the Round Trip Time (RTT) indicating the next (re) transmission opportunity in the uplink HARQ protocol is 8ms. After this 8ms, the UE may send a retransmission 304 of the previous data as directed by the eNB. For further operation, it is assumed that the retransmission 304 of the previously transmitted data packet is again unsuccessful, so that the eNodeB will instruct the UE to perform another retransmission (e.g. send a NACK 305 as feedback). In response thereto, the UE will thus perform further retransmissions 306.
At the top of fig. 3, the subframe numbers and exemplary associations of HARQ processes to subframes are listed. As is evident therefrom, each of the 8 available HARQ processes is associated with a respective subframe cycle. In the exemplary scenario of fig. 3, it is assumed that an initial transmission 302 and its corresponding retransmissions 304 and 306 are handled by the same HARQ process number 5.
The measurement gap for performing measurements at the UE has a higher priority than HARQ retransmissions. Therefore, HARQ retransmission does not occur every time HARQ retransmission collides with the measurement gap. On the other hand, whenever HARQ feedback transmission on PHICH collides with measurement gap, UE assumes ACK as the content of expected HARQ feedback.
There are several fields in the downlink control information to aid HARQ operations:
New Data Indicator (NDI): whenever a transmission of a transport block is scheduled, i.e. also called initial transmission ("switching" means that the NDI bit provided in the associated HARQ information has been changed/switched compared to the value in the previous transmission of this HARQ process)
Redundancy Version (RV): indicating RV selected for transmission or retransmission
MCS: modulation and coding scheme
HARQ operations are complex and will/will not be fully described in the present application, nor is it necessary for a complete understanding of the present application. For example, in 3gpp TS 36.321, release 13.0.0, section 5.4.2, "HARQ operation" incorporated herein by reference, relevant portions of HARQ operation are defined and parts of which will be described below.
5.4.2 HARQ operation
5.4.2.1 HARQ entity
For each serving cell with a configured uplink, there is one HARQ entity at the MAC entity that maintains multiple parallel HARQ processes, allowing transmissions to occur continuously while waiting for successfully or unsuccessfully received HARQ feedback of previous transmissions.
The number of parallel HARQ processes per HARQ entity is specified in [2], section 8.
When the physical layer is configured for uplink spatial multiplexing [2], there are two HARQ processes associated with a given TTI. Otherwise, there is one HARQ process associated with the given TTI.
At a given TTI, if an uplink grant is indicated for the TTI, the HARQ entity identifies the HARQ process(s) for which transmission should occur. It also routes the received HARQ feedback (ACK/NACK information), MCS and resources relayed by the physical layer to the appropriate HARQ process(s).
When configuring TTI bundling, the parameter tti_bundle_size provides the number of TTIs of the TTI BUNDLE. TTI bundling operations rely on HARQ entities to invoke the same HARQ process for each transmission that is part of the same bundle. Within the BUNDLE, HARQ retransmissions are non-adaptive and triggered according to tti_window_size without waiting for feedback from previous transmissions. The bundled HARQ feedback is received only for the last TTI of the BUNDLE (i.e., the TTI corresponding to tti_bundle_size) whether or not transmission in that TTI occurs (e.g., when a measurement gap occurs). The retransmission of the TTI bundle is also a TTI bundle. TTI bundling is not supported when a MAC entity is configured with one or more uplink configured scells.
TTI bundling is not supported for RN communications with E-UTRAN in combination with RN subframe configuration.
For transmission of Msg3 during random access (see sub-clause 5.1.5), TTI bundling is not applicable.
For each TTI, the HARQ entity should:
-identifying the HARQ process(s) associated with this TTI, and for each identified HARQ process:
-if uplink grant has been indicated for this procedure and this TTI:
-if the received grant is not addressed to the temporary C-RNTI on the PDCCH and if the NDI provided in the associated HARQ information has been switched compared to the value in the previous transmission of this HARQ process; or alternatively
-If an uplink grant is received on the PDCCH for the C-RNTI and the HARQ buffer of the identified procedure is empty; or alternatively
-If an uplink grant is received in the random access response:
-if there is a MAC PDU in the Msg3 buffer and an uplink grant is received in the random access response:
-obtaining a MAC PDU to be sent from the Msg3 buffer.
-Else:
-obtaining MAC PDUs to be sent from a "multiplexing and assembling" entity;
-delivering MAC PDU and uplink grant and HARQ information to the identified HARQ process;
-indicating that the identified HARQ process triggers a new transmission.
-Else:
-delivering uplink grant and HARQ information (redundancy version) to the identified HARQ process;
-indicating that the identified HARQ process generates an adaptive retransmission.
Otherwise, if the HARQ buffer of this HARQ process is not empty:
-indicating that the identified HARQ process generates a non-adaptive retransmission.
When determining whether the NDI has been switched compared to the value in the previous transmission, the MAC entity should ignore the NDI received for its temporary C-RNTI in all uplink grants on the PDCCH.
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Uplink HARQ protocol for NB-IoT/eMTC
For NB-IoT and eMTC (Rel-13), an asynchronous UL HARQ protocol has been introduced (and is being discussed for ongoing Rel-14 workings for uplink on unlicensed carriers). Unlike the synchronous uplink HARQ protocol for legacy LTE, the retransmission of NB-IoT or eMTC UEs is adaptive and asynchronous. More particularly, retransmissions need not occur at fixed timing relative to previous HARQ transmissions of the same process, which provides flexibility in explicitly scheduling retransmissions. Furthermore, there will be no explicit HARQ feedback channel (PHICH), i.e. retransmission/initial transmission (NDI distinguishing between initial and retransmission) is indicated by PDCCH. Essentially, the uplink HARQ protocol behavior for NB-IoT or eMTC UEs will be very similar to the asynchronous HARQ protocol for the downlink since Rel-8.
It should be noted that for NB IoT, there will be only one UL HARQ process.
For more information on asynchronous uplink HARQ protocols introduced for NB-IoT/eMTC UEs, refer to section 5.4.2 of 3GPP TS 36.321 V13.1.0 (2016-03) incorporated herein by reference.
Short delay study
Packet data delay is one of the performance metrics that are measured regularly by suppliers, operators, and end users (via speed test applications). Delay measurements are made at all stages of the radio access network system lifecycle when new software versions or system components are verified, when the system is deployed, and when the system is in commercial operation.
Better latency than the previous generations of 3GPP RATs is one performance indicator that directs LTE design. End users now also consider LTE as a system that provides faster internet access and lower data latency than previous generation mobile radio technologies.
In the 3GPP community, much effort has been expended to increase the data rate from LTE-first release (release 8) to the latest release (release 12). Functions such as Carrier Aggregation (CA), 8x8 MIMO, 256QAM, etc. have increased the technical potential of L1 data rates from 300Mbps to 4Gbps. In Rel-13, 3GPP aims to introduce even higher bit rates by introducing up to 32 component carriers in CA.
But w.r.t is especially directed to little further improvement of the delay in the system. Packet data delay is important not only for the perceived responsiveness of the system; but it is also a parameter that indirectly affects throughput. HTTP/TCP is the main application and transport layer protocol suite used on the internet today. Typical sizes for HTTP-based transactions on the internet range from tens of KB to hundreds of MB according to HTTP ARCHIVE (http:// httparchive. Org/tress. Php). Within this size range, the TCP slow start period is a significant part of the total transmission period of the packet stream. During TCP slow start, performance is latency limited. Thus, for this type of TCP-based data transaction, an improved delay may be shown quite easily to improve the average throughput. In addition, in order to achieve a truly high bit rate (in the Gbps range for Rel-13 CA), the UE buffer needs to be dimensioned accordingly. The longer the RTT, the larger the buffer needs to be. The only way to reduce the buffering requirements on the UE and eNB sides is to reduce the delay.
By delay reduction, it is also possible to positively influence the radio resource efficiency. A lower packet data delay may increase the number of possible transmission attempts within a certain delay range; thus, a higher BLER target may be used for data transmission, freeing up radio resources, but still maintaining the same level of robustness for the user under poor radio conditions. The increased number of possible transmissions within a certain delay bound may also translate into a more robust real-time data streaming (e.g., voLTE) if the same BLER target is maintained. This will improve VoLTE voice system capacity.
In terms of increased perceived quality of experience, reduced latency can have more impact on many existing applications: such as gaming, real-time applications like VoLTE/OTT VoIP and video telephony/conferencing.
It is expected that in the future there will be many new applications where the delay becomes more and more critical. Examples include remote control/driving of a vehicle, augmented reality applications such as in smart glasses, or specific machine communication requiring low latency, as well as critical communication.
Various prescheduling strategies can be used to reduce latency to some extent, but they do not necessarily address all efficiency aspects, similar to the shorter Scheduling Request (SR) interval introduced in Rel-9.
It should also be noted that the reduced delay of the user plane data may also indirectly give a shorter call setup/bearer setup time due to faster transport of control signaling.
Therefore, in order to ensure LTE evolution and competitiveness, it is necessary to study and improve packet data delay.
The object of this study is to investigate the improvements of the E-UTRAN radio system in order to:
significantly reducing packet data delay of the LTE Uu air interface of active UE, and
The packet data transmission round trip delay of a UE that is in an inactive state (in a connected state) for a long time is significantly reduced.
Research areas include resource efficiency including air interface capacity, battery life, control channel resources, regulatory impact, and technical feasibility. Both FDD and TDD duplex modes are considered.
As a first aspect, potential benefits of reduced response time and increased TCP throughput due to typical application and use case delay improvements are identified and recorded. In summary, this aspect of the study should show that a delay reduction would be desirable.
As a second aspect, the following fields should be studied and recorded:
Fast uplink access solution:
For active UEs and UEs that are in an inactive state for a longer time but remain in RRC connected state, emphasis is placed on reducing the user plane delay for scheduled UL transmissions and obtaining a more resource efficient solution with protocol and signaling enhancements compared to pre-scheduling solutions allowed by today's standards, both with or without reserving the current TTI length and processing time;
TTI shortening and shortening processing time:
Taking into account the impact on reference signals and physical layer control signaling, evaluating the canonical impact and studying the feasibility and performance of TTI lengths between 0.5ms and one OFDM symbol;
the backward compatibility should be maintained (allowing normal operation of the UE before Rel 13 on the same carrier).
Processing chain functionality for uplink
The processing chain as shown in FIG. 4 is taken from section 5.2.2 of 3GPP TS 36.212 V13.1.0 (2016-03) which is incorporated by reference.
Fig. 4 shows a block diagram including the coding chain function within the physical layer for a single codeword/transport block. The input consists of transport blocks delivered by the MAC layer. For retransmissions of transport blocks, the Redundancy Version (RV) is an input parameter within the "rate matching block". Thus, if retransmissions use different RVs, then at least the blocks "rate matching", "code block concatenation", "data and control multiplexing" and "channel interleaver" need to be processed.
The output of the block "channel interleaver" is used as the "codeword" input for the physical channel processing step shown in fig. 5, taken from section 5.3 of 3GPP TS 36.211 V13.1.0 (2016-03) which is incorporated by reference.
Fig. 5 shows a block diagram including physical channel processing functions within the physical layer. The input includes codeword(s) obtained as a result of the encoding chain described in fig. 5.2.2-1[36.212 ]. It should be noted that for normal (non-MTC or NB-IoT) processing, a "scrambled" block has in its input parameters a transmission subframe index within the radio frame. Thus, even though codeword inputs should be identical, the output of the "scrambling" block is different for different subframe indexes. For retransmissions of transport blocks, the Redundancy Version (RV) is an input parameter within the "rate matching block". Thus, if retransmissions use different RVs, then at least the blocks "rate matching", "code block concatenation", "data and control multiplexing" and "channel interleaver" need to be processed.
Disclosure of Invention
The non-limiting and exemplary embodiments provide improved transmission protocol operation for uplink data packet transmission by a user equipment.
The independent claims provide non-limiting and exemplary embodiments. Advantageous embodiments are limited by the dependent claims.
According to several aspects described herein, transport protocol operation should be improved.
According to another general aspect, there is described a user equipment operating a transmission protocol for uplink data packet transmission in a communication system, the user equipment comprising: a receiver receiving a fast retransmission indicator, FRI, indicating that the base station requests retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and a transmitter that retransmits the data packet using the same transmission parameters as have been used for the previously transmitted data packet, wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, and wherein the transmitter retransmits the indicated portion of the previously transmitted data packet using a transmission power such that a total transmission power for the retransmission is equal to a total transmission power of the previously transmitted data packet.
According to another general aspect, a base station is described that operates a transmission protocol for uplink data packet transmission in a communication system, wherein the base station comprises: a transmitter that transmits a fast retransmission indicator, FRI, wherein the FRI indicates to a user equipment to request retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and a receiver that receives, from a user equipment, a data packet retransmitted with the same transmission parameters as the user equipment has used for the previously transmitted data packet, wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, and wherein the transmitter retransmits the indicated portion of the previously transmitted data packet using a transmit power such that a total transmit power for the retransmission is equal to a total transmit power of the previously transmitted data packet.
According to another general aspect, there is described a method of operating a transmission protocol for uplink data packet transmission in a communication system, the method comprising: receiving a fast retransmission indicator, FRI, wherein the FRI indicates that a base station requests retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and retransmitting the data packet using the same transmission parameters as have been used for the previously transmitted data packet, wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, and wherein the transmitter retransmits the indicated portion of the previously transmitted data packet using a transmit power such that a total transmit power for the retransmission is equal to a total transmit power of the previously transmitted data packet.
According to another general aspect, a base station is described that operates a transmission protocol for uplink data packet transmission in a communication system, wherein the base station includes a transmitter that transmits a fast retransmission indicator. Thus, the fast retransmit indicator indicates to the user equipment whether the base station requests retransmission of a previously transmitted data packet. The base station comprises a receiver that receives, from the user equipment, a retransmitted data packet having the same redundancy version as has been used by the user equipment for a previous transmission of the data packet.
Accordingly, in another general aspect, the technology disclosed herein features a method for operating a transmission protocol in a user equipment for uplink data packet transmission in a communication system. The method includes receiving a fast retransmission indicator, called a FRI, wherein the FRI indicates whether the base station requests retransmission of a previously transmitted data packet. The method further includes retransmitting the data packet using the same redundancy version as that used for the previous transmission of the data packet.
Accordingly, in another general aspect, the technology disclosed herein features a method for operating a transmission protocol in a base station for uplink data packet transmission in a communication system. The method includes transmitting a fast retransmission indicator, called FRI, wherein the FRI indicates to the user equipment whether retransmission of a previously transmitted data packet is requested. The method further comprises receiving, from the user equipment, a retransmitted data packet having the same redundancy version as has been used by the user equipment for a previous transmission of the data packet.
Other benefits and advantages of the disclosed embodiments will be apparent from the description and drawings. The advantages and/or benefits may be provided separately from the various embodiments and features disclosed in the specification and drawings and need not be provided entirely to achieve one or more of them.
These general and specific aspects may be implemented using any combination of systems, methods, and computer programs.
Drawings
Hereinafter, exemplary embodiments are described in more detail with reference to the accompanying drawings and drawings.
Figure 1 shows an exemplary architecture of a 3GPP LTE system,
Figure 2 shows an exemplary downlink resource grid of downlink timeslots of a subframe as defined for 3GPP LTE (release 8/9),
Figure 3 exemplarily illustrates the transport protocol operation between the UE and the eNodeB for uplink transmissions and retransmissions thereof,
Figure 4 schematically illustrates a block diagram comprising the coding chain functions within the physical layer for a single codeword/transport block,
Figure 5 schematically illustrates a block diagram comprising physical channel processing functions within a physical layer,
FIG. 6 illustrates a timing diagram of a transmission request and corresponding transmission, according to an embodiment, an
Fig. 7 illustrates a timing diagram of a transmission request and corresponding transmission in the event of a collision between concurrently requested retransmissions, according to an embodiment.
Detailed Description
As can be seen from fig. 3 and the description in the background section thereof, there is currently a delay of 4ms between PDCCH/PHICH and the corresponding PUSCH uplink transmission. This delay is mainly due to the processing required at the UE side, including the PDCCH/PHICH detection and the coding chain and physical channel processing steps outlined above. Even though shortening the TTI discussed in the context of the short delay study item above may reduce this 4ms delay, the main time savings will be due to the smaller transport block size that allows faster processing and possibly improved hardware/software design. However, even for retransmissions, the savings remain limited because all functional blocks in the transmission chain still need to be processed, especially when retransmissions are performed using different RVs compared to previous transmissions of the same transport block (data packet), as outlined above.
Another delay, currently 4ms long, is the gap between PUSCH transmission and the PDCCH/PHICH for the next potential trigger for the same HARQ process. This gap is caused by the eNB needing to process the PUSCH and attempt to decode it, and in case of unsuccessful decoding attempts, determine again the appropriate scheduling and link adaptation procedure to determine the appropriate set of physical layer transmission parameters (including MCS, number and location of RBs, RV, transmit power) for retransmission, which also needs to take into account the needs of other users for uplink transmissions. Finally, once these parameters are determined, they need to be transmitted to the UE through DCI on (E) PDCCH (for adaptive retransmission) and/or through HI on PHICH (for non-adaptive retransmission).
Even though PHICH can be seen as a compact method of triggering non-adaptive retransmission, the UE still needs to perform a large number of steps before being able to transmit, especially due to the RV version and the subframe dependent scrambling difference.
The object of the present invention is to reduce the delay between the transmission on PUSCH from a UE and the corresponding retransmission indication of an eNodeB. Another object is to also reduce the delay between the indication of the retransmission of the eNodeB and the corresponding retransmission on PUSCH from the UE.
The inventors contemplate the following exemplary embodiments to alleviate one or more of the problems explained above.
A specific implementation of several variants of this embodiment will be implemented in a broad specification given by the 3GPP standard and explained in part in the background section, with specific key features added, as explained below with respect to the described embodiments. It should be noted that this embodiment may be advantageously used in, for example, a mobile communication system, such as the 3GPP LTE-a (release 10/11/12/13) communication system described in the background section above, but is not limited to its use in this particular exemplary communication network.
The explanation should not be construed as limiting the scope of the disclosure but merely as exemplifications of embodiments thereof to better understand the disclosure. The skilled artisan will appreciate that the general principles of the present disclosure as set forth in the claims may be applied to different scenarios and in a manner not explicitly described herein. Several assumptions are made for illustration purposes, but should not limit the scope of the following embodiments.
Hereinafter, embodiments for solving the above-mentioned problem(s) will be described in detail. Different implementations and variations of this embodiment will also be explained.
Embodiments provide a User Equipment (UE) that operates a transmission protocol for uplink data packet transmission in a communication system. According to the transmission protocol, a Fast Retransmission Indicator (FRI) is used to trigger faster retransmissions at the UE with reduced timing in case the PUSCH decoding attempt at the eNodeB is unsuccessful. If such FRI is employed, it is possible to send the retransmission request earlier than would be possible by the eNodeB by using DCI/HI.
In order for the UE to retransmit the data packet faster than is possible in response to the DCI, according to a variant of this embodiment, the UE may use not only the same radio resources for its retransmission of the data packet as if the non-adaptive retransmission was triggered by the HI, but also other exactly the same parameters as they apply to the newly transmitted data packet triggered by the DCI or the HI.
Also, this embodiment provides a base station that operates a transmission protocol for uplink data packet transmission, wherein the FRI is sent to the UE to indicate whether retransmission of a previously transmitted data packet is requested. In response to such a request, the base station receives a retransmitted data packet from the UE, the retransmitted data packet having the same redundancy version as that used for the previously transmitted data packet.
As a general consideration, if the eNodeB intends to trigger a fast retransmission of the data packet, e.g. due to time critical quality of service requirements, it is more important that the retransmission is performed as fast as possible, possibly at the cost of a non-optimal use of the radio channel capacity. As a key aspect to achieving such fast retransmission of data packets, the eNodeB does not need to perform full link adaptation evaluation, since all parameters have been determined for previous transmissions of data packets.
As already explained in the background section, even if the HI is used for retransmission, the redundancy version will be changed for the retransmitted data block. In this case, the redundancy versions loop through a predefined redundancy version sequence, e.g., 0,2, 3, 1. The specific selected redundancy version for retransmission is the input value of the "rate matching" block, as shown in fig. 4. Thus, for each retransmitted data block using a different Redundancy Version (RV), at least the blocks "rate matching", "code block concatenation", "data and control multiplexing" and "channel interleaver" must be processed again. Also, the output of the "channel interleaver" block is then input to the overall physical channel processing, which is shown in fig. 5.
In order to achieve a significant reduction in the time required to transmit a retransmission of a data packet, in one implementation of this embodiment, the UE uses the same redundancy version for its retransmission of the data packet as has been used for the previous transmission of the data packet. Since the UE uses exactly the same subset of transmission parameters for its retransmission of the data packet as for the transmission of the previous DCI trigger, i.e. the same redundancy version as for the previously transmitted data packet, all processing steps involving a change of redundancy version of the data packet may be skipped.
That is, even in the case where only the same RV as the previous DCI (or HI) triggered data packet transmission is used, there is no new "rate matching" and subsequent blocks (as shown in fig. 4) until the beginning of the scrambling needs to be processed (as shown in fig. 5). In other words, for fast retransmissions, it is sufficient if the UE buffers the codewords as they are sent in the most recent transmission and does feed those buffered codewords into the physical channel processing, as shown in fig. 5.
In fig. 6, a timing diagram of a transmission request and corresponding transmission is shown. As can be seen from this figure, the time period between DCI transmission by the eNodeB and corresponding transmission of the data packet by the UE is indicated as time period t0, where time period t0 may be referred to as "third timing". For the uplink HARQ protocol employed since LTE release 8, the time period t0 corresponds to a time period of 4ms, as shown in fig. 3, where a conventional case involving triggering of uplink data transmission by DCI is shown. As can be taken from fig. 6, and contrary to fig. 3, the time period t1 (also shown in fig. 6) between the transmission of data packets by the UE (PUSCH) and the transmission of FRIs by the eNodeB may be equal to or shorter than t0, but in a preferred variant of this embodiment t1 is smaller than time period t0. Although the period t0 may become smaller than 4ms in future further developments, the description of the embodiment assumes that the period t0 is 4ms unless otherwise specified, without limiting the scope of the present invention.
Thus, as another variation of this embodiment, the time period t1, which may be referred to as "first timing", is a fixed time period or a time period semi-statically configurable by the base station, and wherein, preferably, the time period t1 may be less than 4ms.
Note that the FRI may generally indicate at least two states. According to "state 1", the FRI is a "positive FRI" and triggers a fast retransmission, in which case the FRI may be regarded as a negative acknowledgement of the received data packet. According to "state 2", the FRI is a "negative FRI" and does not trigger a faster retransmission, because in this case the FRI may be considered a positive acknowledgement of the received data packet. Thus, a functionally equivalent state interpretation is that a "positive FRI" is equivalent to a FRI carrying a "Negative Acknowledgement (NACK)" and a "negative FRI" is equivalent to a FRI carrying an "Acknowledgement (ACK)". For simplicity and without limiting the scope of the embodiments, the following description uses only the terms "positive FRI" and "negative FRI".
As further deduced from fig. 6, the period t2 (which is defined as the time between a positive FRI sent by the eNodeB and its corresponding PUSCH transmission sent by the UE) must be less than the period t0, t0 being the period between the DCI (or HI) and its corresponding PUSCH transmission. The shorter time period t2 compared to time period t0 is a result of saving computation time at the UE due to using a subset of transmission parameters exactly the same as the previous DCI/HI-triggered transmission for retransmission of the data packet, as described above. The use of identical redundancy versions is illustrated in fig. 6. For example, for both, the DCI-initiated PUSCH transmission and the FRI-initiated PUSCH transmission are performed by using redundancy version rv#0. In other words, rv#0 is determined from DCI-initiated PUSCH transmission and reused by FRI-initiated PUSCH transmission.
Thus, as another variation of this embodiment, the time period t2 (may be referred to as "second timing") is a fixed time period or a time period that is semi-statically configurable by the base station or variable based on corresponding information included in the transmitted/received FRI. Preferably, the time period t2 may be less than 4ms.
According to another implementation of this embodiment, the positive FRI indicates that retransmissions are to be performed with exactly the same additional transmission parameters as were used for the previous transmission of the data packet, which additional exactly the same transmission parameters are then used for retransmitting the data packet by the UE and for receiving the retransmitted data packet at the base station.
According to another implementation of this embodiment, the additional identical transmission parameters to be used for retransmitting the data packet are at least the scrambling code of the previously transmitted data packet. As an advantage of having more identical transmission parameters (such as identical scrambling codes), in addition to the above-mentioned blocks that skip "rate matching" to "channel interleaver", as shown in fig. 4, there is also a "scrambling" block as shown in fig. 5, which also does not require processing of the retransmitted data packet.
In a further variation of this embodiment, additional identical transmission parameters may be reused from a PUSCH transmission initiated by a previous DCI until the point where precoding information is available, i.e., after the block "precoding" in fig. 5. For example, more additional identical transmission parameters may reuse the modulation scheme and layer mapping from the PUSCH transmission initiated by the previous DCI, such that the same transmission scheme is used for retransmission as the previous transmission, i.e., the same number of transmission layers and the same antenna ports are used. In case the FRI does not indicate that a different precoder is to be used, it is most reasonable to use the same precoding vector(s) as in the previous transmission.
But if reusing more identical transmission parameters from a previous DCI initiated PUSCH transmission exceeds the block "precoding" as shown in fig. 5, only a portion of the resources are used for retransmission. For example, a "resource element mapper" block maps data to only a portion of the resources that have been used for a previous transmission, e.g., a fraction of the resource blocks, such as, e.g., 50% of the resource blocks. Equivalently, for fast retransmissions, only the fraction of the output of the "resource element mapper" block is used as input to the "SC-FDMA signal generation" block. Thus, if the UE buffers the output of the previously transmitted "resource element mapper(s)" block and when triggered for partial retransmission, only the corresponding parts are read from the buffer and applied as inputs to SC-FDMA signal generation. Preferably, the fraction for fast retransmission consists of a non-negative integer multiple of the basic time or frequency resource units, such as the "resource blocks" or "resource block groups" defined in TS 36.213. This has the following advantages: unused resources may be optimally assigned to other UEs, i.e. resources caused by fractional resource blocks or groups of resource blocks are not wasted. In addition, the score should be at the resource blockAspects produce bandwidth of PUSCH, where/>And α 2,α3,α5 is a set of non-negative integers. Thus, if the indicated fraction would result in a non-integer number of resource blocks or groups of resource blocks, or if the resulting bandwidth/>Does not satisfy the condition/>Then the UE should preferably round up to a minimum integer number of resource blocks or groups of resource blocks, respectively, less than the indicated fraction, or round up to more than adequateA minimum integer value of the indicated fraction/>
In another variant of this embodiment, as an additional identical transmission parameter, the same "cyclic shift parameter" may be used to generate the reference signal for retransmitting the data packet. In this regard, section 5.5.2 of 3GPP technical standard 36.211 is referred to. The use of the same "cyclic shift parameter" for the generated reference signal results in a further reduction of the total processing time for retransmission. In another variant, the FRI sent by the eNodeB may also include information about the "cyclic shift parameters" to be used by the UE to generate a reference signal for retransmitting the data packet.
It may happen that the most recent transmission of a data block consists not only of UL-SCH data, but also includes Uplink Control Information (UCI) such as ACK/NACK, CSI, etc. As can be seen from fig. 4, this information is added to the data in the block "data and control multiplex". In general, such information is preferably also added in the FRI-triggered retransmission in the same way as the most recent data block transmission. But it is not necessarily reasonable to send exactly the same ACK/NACK or CSI information because the content will be outdated due to the delay between the previous transmission and the triggered retransmission. Thus, alternative embodiments do not include UCI in the retransmission, but instead reserve those resources as if the information were present. Thus, the order of the data block bits may be unchanged, so that no further bit reordering process is required for retransmission.
Also, a portion of the resources of the uplink subframe may contain Sounding Reference Symbols (SRS), preferably at the end of the subframe. In this case, the fast retransmission may also contain SRS as in the previous transmission, or reserve resources (e.g., mute). Thus, the PUSCH-to-resource element mapping may remain unchanged, so no further RE-ordering procedure is required for retransmissions.
Referring to fig. 6 and 7, it is noted that the eNodeB may flexibly determine whether to transmit the FRI, DCI or HI to the UE by requesting retransmission of the data packet from the UE using the FRI or by using the DCI or by using the HI in case the data packet is not successfully received. Also, the UE may flexibly respond to the reception of the FRI, DCI or HI and perform corresponding transmission/retransmission of the data packet based on the received FRI, DCI or HI, as described above.
According to another implementation of this embodiment, the FRI indicates that retransmission of a portion of a previously transmitted data packet is to be performed, optionally wherein the portion is 50% or 25% of the previously transmitted data packet. In this case, the UE retransmits the indicated portion of the previously transmitted data packet. The UE may adjust the transmit power to retransmit a portion of the previously transmitted data packet such that the total transmit power for retransmission is equal to the total transmit power of the previously transmitted data packet, optionally wherein using 50% of the data packets results in a 2-fold increase in the transmit power of the portion of the previously transmitted data packet.
If only a fraction of the frequency resources of the previous transmission is used for the retransmission, then the total power that the UE will send for the partial retransmission will also be a fraction. But to improve the quality of the partially retransmitted data its power may be mutually boosted to a fraction of the frequency resources. For example, if the partial retransmission uses only 50% of the frequency resources, each RE of the partial retransmission may be boosted by 2 times such that the total transmit power is equal when all transmitted REs are used for the partial retransmission and the full retransmission. Such partial retransmissions are particularly attractive if a full retransmission is not required to achieve successful decoding of the transport block, or if the eNodeB intends to use only part of the frequency resources for the retransmission, so that the rest can be scheduled to another UE.
The amount of frequency resources for partial retransmission may be determined according to the following:
1. Semi-static configuration: whenever a fast retransmission is triggered by a positive FRI, the UE looks up the configured value and applies it accordingly.
Indication within fri: the FRI may carry an indicator to determine the amount of partial resources. For example, a first FRI value triggers 50% partial retransmissions, a second FRI value triggers 25% partial retransmissions, a third FRI value triggers full retransmissions (i.e., 100%), and a fourth FRI value does not trigger fast retransmissions. Thus, there will be three positive FRI values and one negative FRI value in this example.
A combination of these is possible, for example, for the eNodeB to configure three different partial retransmission values (possibly comprising 100%), then each positive FRI value points to a corresponding semi-static partial retransmission value (one FRI value indicates no fast retransmission, i.e. one negative FRI value).
In another implementation of this embodiment, the user equipment may include multiple transmit antennas for transmitting the data packets. In this case, the received FRI triggers retransmission of the data packet so that the UE retransmits the data packet to the eNode B using a plurality of transmit antennas. That is, in the case that the transmission contains two transport blocks (codewords) as in SU-MIMO, a positive FRI would preferably indicate that the retransmissions of both transport blocks reuse the transmission buffer as much as possible without excessive PHY reprocessing, as can be appreciated in connection with fig. 5. According to this scenario and referring to fig. 5, reusing the transport buffer in case of retransmitting two transport blocks involves that the blocks shown in fig. 5 need not be processed at all. That is, the retransmission of two transport blocks occurs just after the corresponding "SC-FDMA signal generation" block and can be sent directly to the eNodeB without further processing.
On the eNodeB side, where multiple antennas can also be used, when transmitting the FRI that triggers retransmission of a transport block, the retransmitted transport block is received at the eNodeB using multiple receive antennas.
But triggering retransmission of two transport blocks by (single) FRI comes at the cost of radio resource efficiency and signal-to-noise ratio. Thus, an alternative embodiment of this embodiment would trigger retransmission of one transport block per FRI such that retransmission of one transport block to the eNodeB and reception of one transport block at the eNodeB is performed by using multiple transmit antennas. It should be noted that in this case, more processing is required at the UE until SC-FDMA signals are available for transmission. That is, referring to fig. 5, if the FRI triggers retransmission of only one transport block, this involves processing of "layer map" blocks until "SC-FDMA signal generation" blocks.
The above description relates to the behaviour for retransmissions, according to which it is assumed that the same transport block data is used in transmission and retransmission, i.e. implying that retransmissions apply to the same HARQ process. There may be multiple concurrently schedulable HARQ processes-following synchronous or asynchronous protocols.
In both cases, a fast retransmission will occur at time "# t_pusch" in the TTI, as shown in fig. 7. Thus, PUSCH transmission at time "# t_pusch" may be triggered by a positive FRI at time "# t_pusch-t2" or by DCI (or HI) at time "# t_pusch-t0" and is generally used for different HARQ processes. Thus, in fig. 7, different HARQ processes P0 and P1 are illustrated. In the exemplary case shown in fig. 7, HARQ process P0 involves a FRI-initiated retransmission at time "# t_pusch", while HARQ process P1 involves a DCI-initiated retransmission at time "# t_pusch-t 0".
As further shown in fig. 7, retransmissions for both HARQ processes P0 and P1 will result in retransmissions at time "#t_pusch". But in order to avoid transmission collisions, the UE needs to decide what it should do at time "#t_pusch". The first option is to continue to perform retransmissions for HARQ process P0, i.e. follow the FRI trigger received at time "# t_pusch-t 2". The second option is to continue to perform retransmissions for HARQ process P1, i.e. follow the DCI (or HI) received at time "#t_pusch-t 0".
In this respect, a preferred implementation of this embodiment involves a specific behavior of the UE such that, in case a request for retransmission of a data packet by the FRI is received and a request for transmission of another data packet by the DCI or the HI is simultaneously performed, it follows the request of the FRI (i.e. the first option mentioned before) and ignores the request of the DCI or the HI.
As shown in the background section, when there is a collision between the HI and the DCI, the UE follows the DCI and ignores the HI. But in contrast, where provided by alternative implementations of the embodiments, fast retransmissions should be followed and DCI (or HI) should be ignored. This is because the positive FRI is already transmitted at a later point in time than the DCI corresponding to the same subframe. Thus, it should be assumed that the eNodeB will only send a positive FRI if it intends for the UE to follow the positive FRI instead of DCI. Otherwise, it does not trigger retransmission by the positive FRI for that subframe.
As already described in connection with fig. 6, also for the case where the UE follows the request of the FRI to avoid transmission collision, as shown in fig. 7, the exact same redundancy version is used for both, and both PUSCH transmission initiated by DCI and PUSCH transmission initiated by FRI are performed by using redundancy version rv#0. In other words, rv#0 is determined according to DCI-initiated PUSCH transmission and reused by FRI-initiated PUSCH transmission.
Also, in another variation of this embodiment, the FRI further includes a HARQ process number indicator to indicate the particular HARQ process used by the sender for the previous transmission of the data packet.
In the following table, the UE behavior is shown for several cases with respect to the content of the received FRI and DCI/HI.
In the following table, the content regarding the received FRI and DCI/HI shows alternative UE behavior for several cases.
Referring to the description provided above, according to one variation of this embodiment, the FRI may indicate at least one of the following elements:
Whether or not a fast retransmission (positive FRI or negative FRI, or alternatively NACK or ACK) is triggered;
in case of triggered fast retransmission: an HARQ process number indication for the triggered retransmission;
in case of triggered fast retransmission: a fractional retransmission parameter indicating a portion of the requested data block to be retransmitted;
in case of triggered fast retransmission: an indication of the previous period t2 until the UE should transmit accordingly.
According to another implementation of the embodiment, the UE receives the FRI in radio resources for receiving the HI, or the FRI as DCI (e.g. in DCI format 7), or in radio resources of a preconfigured common search space, or in preconfigured radio resources of a user equipment specific search space.
In general, the FRI may be sent by one of the following ways:
In the same RE(s) of which the UE expects to find PHICH (but in a different subframe if the time period t1 is smaller than the time between PUSCH transmission and the subframe carrying the corresponding HI), i.e. in the RE(s) of REGs within the control channel region belonging to subframe/TTI, or
Among the RE(s) belonging to the common search space for DCI, i.e. among REs where all UEs detect FRI, or
In DCI, the FRI is preferably multiplexed for multiple UEs and/or subframes. For example, the DCI may contain four FRIs, with the first FRI applicable to UE1, the second FRI applicable to UE2, and so on. Especially for TDD systems, several FRIs may be multiplexed or bundled into DCI for one UE, such that for example the first four FRIs are applicable to four PUSCH transmissions for UE1, the next three FRIs are applicable to three PUSCH transmissions for UE2, and so on. In case of multiplexing FRI for a plurality of UEs, DCI is preferably transmitted in a common search space. In case of transmitting only the FRI for one UE, the DCI is preferably transmitted in the UE-specific search space.
As a variation of this embodiment, instead of including one or more of the above into the FRI, one or more of the above may be used to determine the RE(s) that transmit the FRI. For example, the HARQ process may determine RE(s) that transmit the FRI. The UE will then monitor the multiple FRI resources and preferably evaluate only the FRI received at the strongest power.
As described with respect to several variations of the above embodiments, in contrast to retransmissions triggered by the HI described in the background section, a positive FRI does not imply an implicit or explicit change in the retransmission of the RV. But as another variation of this embodiment, the FRI-triggered retransmission should not affect the potential RV determination rules for non-adaptive retransmissions of PHICH. As indicated previously in the background section, retransmissions triggered by PHICH implicitly switch between RV {0,2,3,1 }. According to this variant, the positive FRI should be ignored for the purpose of RV determination for later non-adaptive retransmissions, i.e. RV switching/cycling should only consider the RV of the previous DCI/HI triggered (re-) transmission.
As another variation of this embodiment, if PUSCH does not occupy a complete 1ms TTI, but a short TTI (as discussed in the short delay study item above), then the transport block is smaller than the 1ms TTI, except for the use of FRI as described above, so the decoding result (OK/fail) at eNodeB will be available faster. Thus, in this case, the FRI may be transmitted earlier than DCI/HI in a conventional system.
As another implementation of this embodiment, the previous transmission of the data packet may be "initial transmission of the data packet" or "retransmission of the data packet".
In accordance with embodiments of the present disclosure, at least user equipment, base stations and methods of operating a transmission protocol are disclosed.
According to a user equipment of the present disclosure, operating a transmission protocol for uplink data packet transmission in a communication system, wherein the user equipment comprises: a receiver operable to receive a fast retransmission indicator, called FRI, wherein the FRI indicates whether a base station requests retransmission of a previously transmitted data packet; and a transmitter operable to retransmit the data packet using the same redundancy version that has been used for the previous transmission of the data packet.
The user equipment according to the present disclosure, wherein the FRI indicates that the retransmission is to be performed with exactly the same additional transmission parameters as used for the previous transmission of the data packet; and wherein the transmitter is further operable to retransmit the data packet using exactly the same additional transmission parameters as were used for the previous transmission of the data packet.
The user equipment according to the present disclosure, wherein the additional identical transmission parameter to be used for retransmitting the data packet is at least a scrambling code of the previously transmitted data packet.
The user equipment according to the present disclosure, wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, optionally wherein the portion is 50% or 25% of the previously transmitted data packet; and wherein the transmitter is further operable to retransmit the indicated portion of the previously transmitted data packet.
The user equipment according to the present disclosure, wherein the transmitter is further operable to retransmit the portion of the previously transmitted data packet using a transmit power such that a total transmit power for the retransmission is equal to a total transmit power of the previously transmitted data packet, optionally wherein using 50% of the data packet results in a 2-fold increase in transmit power of the portion of the previously transmitted data packet.
The user equipment according to the present disclosure, wherein the receiver is further operable to receive the FRI at a first timing after the transmission of the previous data packet, wherein the first timing is fixed or semi-statically configurable by the base station.
The user equipment of the present disclosure, wherein the transmitter is further operable to transmit the retransmission of the data packet at a second timing after the receiver receives the FRI; wherein the second timing is fixed, semi-statically configurable by the base station, or variable based on corresponding information included in the received FRI.
A user equipment according to the present disclosure, wherein retransmission of data packets may also be triggered by downlink control information, referred to as DCI, and/or a HARQ indicator, referred to as HI; wherein a first time period between the previous transmission of the data packet and the reception of the FRI and/or a second time period between the reception of the FRI and the retransmission of the data packet is less than a third time period between the reception of DCI or HI and its corresponding retransmission of the data packet, optionally wherein at least one of the first time period and the second time period is less than 4ms.
The user equipment of the present disclosure, wherein, in case the receiver receives a request to perform the retransmission of the data packet through the FRI and a request to simultaneously perform transmission of another data packet through the DCI or HI, the transmitter is further operable to follow the request through the FRI and ignore the request through the DCI or HI.
The user equipment according to the present disclosure, wherein the FRI further comprises a HARQ process number indicator for indicating the HARQ process used by the transmitter for the previous transmission of the data packet.
The user equipment according to the present disclosure, wherein the previous transmission of the data packet is an initial transmission or retransmission of the data packet.
The user equipment according to the present disclosure, wherein the receiver is further operable to receive the FRI in radio resources for receiving the HI, or to receive the FRI as DCI, or to receive the FRI in preconfigured radio resources of a common search space, or to receive the FRI in preconfigured radio resources of a user equipment-specific search space.
A user equipment according to the present disclosure, wherein when the user equipment uses multiple transmit antennas for transmission of data packets: the receiver is further operable to receive the FRI triggering retransmission of the data packet; and the transmitter is further operable to retransmit the data packet to the base station using the plurality of transmit antennas; or wherein: the receiver is further operable to receive the FRI triggering retransmission of one of the data packets; and the transmitter is further operable to retransmit one of the data packets to the base station using the plurality of transmit antennas.
According to the base station of the present disclosure, a transmission protocol for uplink data packet transmission in a communication system is operated, wherein the base station comprises: a transmitter operable to transmit a fast retransmission indicator, referred to as a FRI, wherein the FRI indicates to a user equipment whether to request retransmission of a previously transmitted data packet; and a receiver operable to receive the retransmitted data packet from the user equipment using the same redundancy version as has been used by the user equipment for the previous transmission of the data packet.
The base station according to the present disclosure further includes: a processor operable to determine whether to request retransmission of the data packet from the user equipment by using the FRI, or by using downlink control information called DCI, or by using a HARQ indicator called HI if the data packet is not successfully received; wherein the transmitter is further operable to transmit either the FRI, or the DCI or the HI.
A base station according to the present disclosure, wherein the FRI indicates to the user equipment to perform the retransmission with exactly the same additional transmission parameters as used for the previous transmission of the data packet; and wherein the receiver is further operable to receive the retransmitted data packet, wherein an additional transmission parameter is used for the retransmitted data packet, the additional transmission parameter being identical to a transmission parameter used for the previous transmission of the data packet.
The base station according to the present disclosure, wherein the additional identical transmission parameter for the retransmitted data packet is at least a scrambling code of the previously transmitted data packet.
A base station according to the present disclosure, wherein the FRI indicates to the user equipment to perform retransmission of a portion of the previously transmitted data packet, optionally wherein the portion is 50% or 25% of the previously transmitted data packet; and wherein the receiver is further operable to receive the retransmitted portion of the previously transmitted data packet.
The base station according to the present disclosure, wherein the transmitter is further operable to transmit the FRI at a first timing after the reception of the previous data packet, wherein the first timing is fixed or semi-statically configurable by the base station.
A base station according to the present disclosure, wherein the receiver is further operable to receive the retransmission of the data packet at a second timing after the transmitter transmits the FRI; wherein the second timing is fixed, semi-statically configurable by the base station or variable based on corresponding information included in the transmitted FRI.
A base station according to the present disclosure, wherein retransmission of data packets can also be triggered by the base station via the DCI and/or the HI; wherein a first time period between the reception of the previously transmitted data packet and the transmission of the FRI, and/or a second time period between the transmission of the FRI and the reception of the retransmission of the data packet is less than a third time period between the transmission of DCI or HI and the reception of the corresponding retransmitted data packet, optionally wherein at least one of the first time period and the second time period is less than 4ms.
The base station according to the present disclosure, wherein the FRI further comprises a HARQ process number indicator for indicating the HARQ process used by the user equipment for the previous transmission of the data packet.
The base station according to the present disclosure, wherein the previous transmission of the data packet by the user equipment is an initial transmission or retransmission of the data packet.
The base station according to the present disclosure, wherein, when the base station uses a plurality of receiving antennas: the transmitter is further operable to transmit the FRI triggering retransmission of the data packet; and the receiver is further operable to receive the retransmitted data packet using the plurality of transmit antennas; or wherein: the transmitter is further operable to transmit the FRI triggering retransmission of one of the data packets; and the receiver is further operable to receive a retransmitted one of the data packets using the plurality of receive antennas.
A method according to the present disclosure for operating a transmission protocol for uplink data packet transmission in a communication system in a user equipment, wherein the method comprises the steps of: receiving a fast retransmission indicator, called FRI, wherein the FRI indicates whether a base station requests retransmission of a previously transmitted data packet; and retransmitting the data packet using the same redundancy version that has been used for the previous transmission of the data packet.
A method according to the present disclosure, wherein the FRI indicates that the retransmission is to be performed with exactly the same additional transmission parameters as used for the previous transmission of the data packet; and wherein the method further comprises the step of retransmitting the data packet using exactly the same additional transmission parameters as used for the previous transmission of the data packet.
The method according to the present disclosure, wherein the additional identical transmission parameter to be used for retransmitting the data packet is at least a scrambling code of the previously transmitted data packet.
A method according to the present disclosure, wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, optionally wherein the portion is 50% or 25% of the previously transmitted data packet; and wherein the method further comprises the step of retransmitting the indicated portion of the previously transmitted data packet.
The method according to the present disclosure further comprises the steps of: the transmit power is used for the retransmission of the portion of the previously transmitted data packet such that the total transmit power for the retransmission is equal to the total transmit power of the previously transmitted data packet, optionally wherein using 50% of the data packets results in a 2-fold increase in the transmit power of the portion of the previously transmitted data packet.
The method according to the present disclosure further comprises the step of receiving the FRI at a first timing after the transmission of the previous data packet, wherein the first timing is fixed or semi-statically configurable by the base station.
The method according to the present disclosure further comprising the step of transmitting the retransmission of the data packet at a second timing after the FRI is received by the receiver; wherein the second timing is fixed, semi-statically configurable by the base station or variable based on corresponding information included in the received FRI.
According to the method of the present disclosure, wherein the retransmission of the data packet may also be triggered by downlink control information, called DCI, and/or a HARQ indicator, called HI; wherein a first time period between the previous transmission of the data packet and the reception of the FRI and/or a second time period between the reception of the FRI and the retransmission of the data packet is less than a third time period between the reception of DCI or HI and its corresponding retransmission of the data packet, optionally wherein at least one of the first time period and the second time period is less than 4ms.
The method according to the present disclosure, wherein, in case a request to perform the retransmission of the data packet through the FRI and a request to simultaneously perform the transmission of another data packet through the DCI or the HI are received by the user equipment, the method further comprises the step of following the request through the FRI and ignoring the request through the DCI or the HI.
The method according to the present disclosure, wherein the FRI further comprises a HARQ process number indicator for indicating the HARQ process used by the user equipment for the previous transmission of the data packet.
The method according to the present disclosure, wherein the previous transmission of the data packet is an initial transmission or retransmission of the data packet.
The method according to the present disclosure further comprises the steps of: the FRI is received in radio resources for receiving the HI, or is received as DCI, or is received in preconfigured radio resources of a common search space, or is received in preconfigured radio resources of a user equipment specific search space.
The method according to the present disclosure, wherein when the user equipment uses a plurality of transmit antennas for transmission of data packets, the method further comprises the steps of: receiving the FRI triggering retransmission of the data packet; and retransmitting the data packet to the base station using the plurality of transmit antennas; or: receiving the FRI triggering retransmission of any one of the data packets; and retransmitting one of the data packets to the base station using the plurality of transmit antennas.
A method for operating a transmission protocol for uplink data packet transmission in a communication system in a base station according to the present disclosure, wherein the method comprises the steps of: transmitting a fast retransmission indicator, called FRI, wherein the FRI indicates to the user equipment whether retransmission of previously transmitted data packets is requested; and receiving the retransmitted data packet from the user equipment using the same redundancy version as has been used by the user equipment for the previous transmission of the data packet.
The method according to the present disclosure further comprises the steps of: in case of unsuccessful reception of the data packet, determining whether retransmission of the data packet is requested from the user equipment by using the FRI, or by using downlink control information called DCI, or by using a HARQ indicator called HI; and transmitting either the FRI, or the DCI, or the HI.
A method according to the present disclosure, wherein the FRI indicates to the user equipment to perform the retransmission with exactly the same additional transmission parameters as used for the previous transmission of the data packet; and wherein the method further comprises the step of receiving the retransmitted data packet, wherein an additional transmission parameter is used for the retransmitted data packet, the additional transmission parameter being identical to a transmission parameter used for the previous transmission of the data packet.
The method according to the present disclosure, wherein the additional identical transmission parameter for the retransmitted data packet is at least a scrambling code of the previously transmitted data packet.
The method according to the present disclosure, wherein the FRI indicates to the user equipment to perform retransmission of a portion of the previously transmitted data packet, optionally wherein the portion is 50% or 25% of the previously transmitted data packet; and wherein the method further comprises the step of receiving the retransmission portion of the previously transmitted data packet.
The method according to the present disclosure further comprises the step of transmitting the FRI at a first timing after the reception of the previous data packet, wherein the first timing is fixed or semi-statically configurable by the base station.
The method according to the present disclosure further comprises the steps of: receiving the retransmission of the data packet at a second timing after the transmitter transmits the FRI; wherein the second timing is fixed, semi-statically configurable by the base station or variable based on corresponding information included in the transmitted FRI.
A method according to the present disclosure, wherein retransmission of a data packet can also be triggered by the base station via the DCI and/or the HI; wherein a first time period between the reception of the previously transmitted data packet and the transmission of the FRI, and/or a second time period between the transmission of the FRI and the reception of the retransmission of the data packet is less than a third time period between the transmission of DCI or HI and the reception of the corresponding retransmitted data packet, optionally wherein at least one of the first time period and the second time period is less than 4ms.
The method according to the present disclosure, wherein the FRI further comprises a HARQ process number indicator for indicating the HARQ process used by the user equipment for the previous transmission of the data packet.
The method according to the present disclosure, wherein the previous transmission of the data packet by the user equipment is an initial transmission or retransmission of the data packet.
The method according to the present disclosure, wherein when the base station uses a plurality of transmitting antennas, the method further comprises the steps of: transmitting the FRI triggering retransmission of the data packet; and receiving the retransmitted data packet using the plurality of receive antennas; or: transmitting the FRI triggering retransmission of one of the data packets; and receiving a retransmitted one of the data packets using the plurality of receive antennas.
Hardware and software implementations of the present disclosure
Other exemplary embodiments relate to implementing the various embodiments described above using hardware, software, or software in conjunction with hardware. In this regard, a user terminal (mobile terminal) and an eNodeB (base station) are provided. The user terminal and the base station are adapted to perform the methods described herein, including corresponding entities suitably involved in the methods, such as receivers, transmitters, processors.
It is also to be appreciated that various embodiments may be implemented or performed using computing devices (processors). The computing device or processor may be, for example, a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic device, or the like. Various embodiments may also be implemented or embodied by a combination of these devices. In particular, each of the functional blocks used in the description of each of the embodiments described above may be implemented by an LSI as an integrated circuit. They may be formed separately as chips, or may be formed as one chip so as to include part or all of the functional blocks. They may include data inputs and outputs coupled thereto. The LSI herein may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the difference in integration level. The technique of implementing the integrated circuit is not limited to LSI and may be implemented by using dedicated circuits or general-purpose processors. Further, an FPGA (field programmable gate array) which can be programmed after LSI manufacture or a reconfigurable processor in which connection and setting of circuit cells placed inside the LSI can be reconfigured may be used.
Furthermore, the various embodiments may also be implemented by software modules executed by a processor or directly in hardware. Combinations of software modules and hardware implementations are also possible. The software modules may be stored on any kind of computer readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disk, CD-ROM, DVD, etc. It should also be noted that the individual features of the different embodiments may be combined individually or arbitrarily in relation to the features of the other embodiments.
Those skilled in the art will recognize that many variations and/or modifications may be made to the present disclosure as shown in the specific embodiments. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Claims (15)
1. A user equipment operating a transmission protocol for uplink data packet transmission in a communication system, the user equipment comprising:
A receiver that receives a fast retransmission indicator, FRI, wherein the FRI indicates that a base station requests retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and
A transmitter retransmitting the data packet using the same transmission parameters as have been used for the previously transmitted data packet,
Wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, and wherein the transmitter retransmits the indicated portion of the previously transmitted data packet using a transmit power such that a total transmit power for the retransmission is equal to a total transmit power of the previously transmitted data packet.
2. The user equipment of claim 1, wherein the FRI indicates that retransmission is to be performed using the same redundancy version as used for the previously transmitted data packet, and wherein the transmitter further retransmits the data packet using the same redundancy version as used for the previously transmitted data packet.
3. The user equipment of claim 2, wherein the same transmission parameters comprise a scrambling code of the previously transmitted data packet.
4. The user equipment of claim 1, wherein the portion is 50% or 25% of the previously transmitted data packet.
5. The user equipment of claim 4, wherein using 50% of the data packets causes an increase in transmit power of the portion of the previously transmitted data packets by a factor of 2.
6. The user equipment of claim 1, wherein the receiver further receives the FRI at a first timing after transmission of a previously transmitted data packet, wherein the first timing is fixed or semi-statically configurable by a base station.
7. The user equipment of claim 1, wherein the transmitter further transmits a retransmission of the data packet at a second timing after the receiver receives the FRI; and wherein the second timing is fixed, semi-statically configurable by the base station, or variable based on corresponding information included in the received FRI.
8. The user equipment of claim 1, wherein retransmission of the data packet is triggered by downlink control information, DCI, or a HARQ indicator, HI, and wherein a first time period between previous transmission of the data packet and reception of the FRI or a second time period between reception of the FRI and retransmission of the data packet is less than a third time period between reception of the DCI or the HI and retransmission of its corresponding data packet, wherein at least one of the first time period and second time period is less than 4ms.
9. The user equipment of claim 8, wherein the transmitter further follows the request through the FRI and ignores the request through the DCI or the HI in case the receiver receives the request through the FRI to perform retransmission of the data packet and the request through the DCI or the HI to simultaneously perform transmission of another data packet.
10. The user equipment of claim 1, wherein the FRI further comprises a HARQ process number indicator for indicating a previously transmitted HARQ process used by the transmitter for the data packet.
11. The user equipment of claim 1, wherein the previous transmission of the data packet is an initial transmission or retransmission of the data packet.
12. The user equipment of claim 1, wherein the receiver further receives the FRI in radio resources for receiving HI, or receives the FRI as DCI, or receives the FRI in preconfigured radio resources of a common search space, or receives the FRI in preconfigured radio resources of a user equipment-specific search space.
13. The user equipment of claim 1, wherein when the user equipment uses a plurality of transmit antennas to transmit the data packet:
the receiver also receives a FRI triggering retransmission of the data packet; and
The transmitter also retransmits the data packet to the base station using the plurality of transmit antennas;
Or wherein:
the receiver also receives a FRI triggering retransmission of one of the data packets; and
The transmitter also retransmits one of the data packets to the base station using the plurality of transmit antennas.
14. A base station operating a transmission protocol for uplink data packet transmission in a communication system, wherein the base station comprises:
a transmitter that transmits a fast retransmission indicator, FRI, wherein the FRI indicates to a user equipment to request retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and
A receiver that receives, from a user equipment, data packets retransmitted with the same transmission parameters as the user equipment has used for the previously transmitted data packets,
Wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, and wherein the receiver receives the indicated portion of the previously transmitted data packet that was retransmitted using a transmit power such that a total transmit power for the retransmission is equal to a total transmit power of the previously transmitted data packet.
15. A method in a user equipment of operating a transmission protocol for uplink data packet transmission in a communication system, the method comprising:
Receiving a fast retransmission indicator, FRI, wherein the FRI indicates that a base station requests retransmission of a previously transmitted data packet using the same transmission parameters as the previously transmitted data packet; and
The data packets are retransmitted using the same transmission parameters as have been used for the previously transmitted data packets,
Wherein the FRI indicates that retransmission of a portion of the previously transmitted data packet is to be performed, and wherein the indicated portion of the previously transmitted data packet is retransmitted using a transmit power such that a total transmit power for the retransmission is equal to a total transmit power of the previously transmitted data packet.
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| CN110972317B (en) * | 2018-09-28 | 2022-06-28 | 华为技术有限公司 | Communication method and device |
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| US20240056229A1 (en) | 2024-02-15 |
| US20230118789A1 (en) | 2023-04-20 |
| US10958382B2 (en) | 2021-03-23 |
| CN109155704B (en) | 2021-12-10 |
| US11588584B2 (en) | 2023-02-21 |
| CN114244480A (en) | 2022-03-25 |
| EP3455971B1 (en) | 2021-11-17 |
| JP6644912B2 (en) | 2020-02-12 |
| US20190149273A1 (en) | 2019-05-16 |
| EP3455971A1 (en) | 2019-03-20 |
| US20210167898A1 (en) | 2021-06-03 |
| US11831441B2 (en) | 2023-11-28 |
| CN109155704A (en) | 2019-01-04 |
| JP2019515535A (en) | 2019-06-06 |
| EP3455971A4 (en) | 2019-05-22 |
| WO2017193376A1 (en) | 2017-11-16 |
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